Cytophotometry refers to the photometric measurement of cells using a microscope. Current cytophotometers used for research are relatively expensive, often slow, and many of the commercial instruments do not have the flexibility required for biomedical research. During the past decade charge-coupled device (CCD) technology has developed and these new devices might be useful for cytophotometry. CCD area imaging cameras feature high speed, high sensitivity, low noise and a fixed geometry that makesthis new technology attractive for research applications using cytophotometry. This proposal presents a plan to test the feasibility of using a 256x256 element CCD image camera for single cell cytophotometry. The CCD camera will be used in conjunction with a Zeiss Universal microscope and a Digital Equipment Corporation LSI 11/23 computer. Computer programs will be developed for acquisition of data from the CCD device, image segmentation, image display, and calculation of integated optical density, cell area, and shape features. Precision and accuracy of the measurements will be made by comparing results obtained with the CCD camera with measurements on the same cells made with a Zeiss scanning stage cytophotometer using the HIDACSYS computer programs. The usefulness and speed of CCD-based cytophotometry will be tested by using the instrument in a large study to determine the effects of immunostimulants on the lysosomal enzyme content of alveolar macrophages cultured in tissue culture. If application of CCD technology to cytophotometry proves useful, future biomedical research will benefit by having a lower cost, faster and more flexible instrument.